Compressor

ABSTRACT

An axial compressor is provided. The compressor has an annular flow channel, in which adjustable blades of a blade ring that extend through the flow channel are rotatably mounted. Each blade has a lug on the rotor-side of the vane for mounting an inner ring. In order to provide a wear-free, self-centering inner ring, the ring is designed as a split ring with two opposing ends and a spring element for spreading the split ring.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2011/061486 filed Jul. 7, 2011 and claims the benefit thereof. The International Application claims the benefits of European application No. 10007062.2 filed Jul. 8, 2010, both of the applications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a compressor having a housing, which defines the radially outer limit of an annular flow duct and in which guide vanes of a vane ring extending radially through the flow duct are pivotally mounted, wherein each guide vane on the housing side comprises a first pivot extending through the housing and on the rotor side comprises a second pivot extending into an inner ring.

BACKGROUND OF THE INVENTION

Known compressors of modern gas turbines comprise one or more compressor stages, the guide vanes of which are adjustable. Here the guide vanes assigned to a corresponding ring are adjustable about their longitudinal axis, in order to regulate the mass flow. The capacity for regulating the mass flow gives the compressor a larger working range. For pivotally affixing the guide vanes of such compressor stages, pivots are provided at each of the two blade ends of the guide vanes. Here the outer pivot is supported in the annular housing and the inner pivot in a so-called inner ring. In this case the inner ring is held by all the guide vanes. The inner ring is positioned centrally in relation to the rotor axis via the radial positioning of the outer pivots in the housing. Here, however, the radial adjustment of the vanes serves not only to position the inner ring in relation to the rotor but at the same time also to set the gaps between the blades of the adjustable guide vanes and the external housing and the inner ring, so that in the process of adjusting the blade this does not touch the boundary wall of the flow duct.

Since the known design for holding the inner ring provides for a positive radial interlock between the guide vanes and the inner ring, greater mechanical stresses can occur inside the respective inner ring bearing, which can cause considerable wear to the bearing bushes used there. Here the mechanical stresses during operation may be also exacerbated by thermal stresses.

U.S. Pat. No. 2,671,634 discloses an alternative variant of the bearing of adjustable guide vanes. The arrangement shown therein comprises an inner ring divided into two equal segments. The ends of the segments here rest loosely against one another in a tongue-and-groove connection, the inner pivots of the adjustable guide vanes being supported directly in radial bores of the inner ring. Each segment is thereby supported by those in the associated guide vanes, which can also lead to increased wear.

SUMMARY OF THE INVENTION

The object of the invention in therefore to provide a compressor having a fastening arrangement for guide vanes which are capable of pivoting about their longitudinal axis and an inner ring support of which is relatively free from wear and at the same time allows easy positioning of the inner ring in relation to the rotor.

The object of the invention is achieved by a compressor, in which the inner ring is embodied as a split ring having two opposing ends and is provided with a spring element for spreading the ring gap. For this purpose it is proposed to fit a preferably encapsulated spring element in the area of the ring gap. With the upper housing part and the lower housing part in the assembled state, this affords a radial prestressing of the inner ring. The radial prestressing serves to press the inner ring against the second pivots of the guide vanes. This makes it possible to dispense with the radial fixing of the inner ring to all guide vanes. This means that the second pivots extending into the inner ring are merely inserted into the respective bores or recesses from outside—the positive radial interlock hitherto provided can be dispensed with. Consequently the guide vanes can be equipped with a second pivot which is disposed radially inside and is of a purely cylindrical design. The same applies to the bores in the inner ring, which receive the pivots and which according to the invention no longer comprise a continuous circumferential flange for the positive interlock. It is of particular advantage here that potential distortions of the inner ring are now avoided due to the absence of radial latching. In addition the simplified design of the inner bearing of the guide vanes reduces the assembly time.

In thermally transient operation the thermal expansions of the inner ring and all guide vanes are moreover compensated for by the spring element, which reduces the stresses between the inner ring and the inner points of support of the guide vanes and reduces wear to the bearings.

Introducing a spring element consequently allows the inner ring to be designed as a self-supporting and self-centering system, in which only the adjustable guide vanes arranged in the lower half of the vane ring then support the so-to-speak floating inner ring.

A further advantage of the invention is that owing to the self-centering support of the inner ring the adjusting device for the radial positioning of the guide vanes in the housing can even be dispensed with. This simplifies the compressor and owing to the smaller number of components used reduces the likelihood of the compressor failing.

Advantageous developments are specified in the dependent claims.

According to a first advantageous development of the invention the two ends of the split ring comprise opposing first sockets, which are in the nature of blind holes and in which the spring element is seated. A relatively simple design for spreading the split ring can thereby be specified, in which the spring element is embodied as a coil spring, for example. The coil spring is prevented from slipping, since it is seated in the sockets.

In order to protect the spring element from dirt it is advantageous if this is of encapsulated design.

Relative movements of the two ends of the inner ring in an axial direction can be prevented if these ends are axially locked. This can be done with parallel keys, for example, which predefine the axial positioning of the two opposing ends of the split ring. For this purpose, for example, the parallel keys are likewise arranged in sockets provided for this purpose in both end faces of the gap in the inner ring.

According to a further advantageous development the inner ring comprises at least two segments. The segments here preferably extend over an arc length of 180°. This allows a relatively easy assembly of the guide vanes in a compressor.

A collared bushing may be provided as a wearing lubricant between the second pivots and each of the bores of the inner ring receiving the pivots. In order to prevent fouling of the friction bearing of the pivot in the respective bore of the inner ring, it is proposed that a continuous circumferential groove be provided on the second pivot, in which groove a sealing ring, for example an O-ring seating therein, is arranged. This reduces the wear to the radially inner bearing.

An inner ring or segment that is relatively easy to produce can be specified if these are axially dividable. The parts of the segment or the inner ring can be screwed together, for example, or also welded together. However, the segment or the inner ring is preferably undivided axially.

According to the invention a stationary gas turbine having a housing dividable into equal parts and intended for generating power is in particular equipped with an inventive compressor according to the aforementioned developments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained further with reference to the exemplary embodiment represented in the drawing, in which, in particular:

FIG. 1 shows a cross section through a detail of the compressor having compressor guide vanes rotatably supported at both ends and capable of pivoting about their longitudinal axis;

FIG. 2 schematically shows an inner ring embodied as a split ring and

FIG. 3 shows, by way of example, a spring element arranged in the gap between the two opposing ends of the split ring.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross section through a compressor 10 of axial-flow type in the axial portion of guide vanes 14 capable of pivoting about their longitudinal axis 12. The guide vanes 14 may be inlet guide vanes of the compressor 10, for example. However, they may also form part of vane rings of subordinate compressor stages situated downstream thereof. The guide vanes 14 comprise an aerodynamically curved blade 16 (represented only in part), at the radially inner end 18 of which a circular platform 20 is arranged. The platform 20 merges into a first cylindrical portion 22, in which a circumferential groove 24 is arranged for receiving a sealing O-ring. Adjoining the first portion 22 is a concentric second portion 23 of smaller diameter. Both portions 22, 23 are part of a pivot 26 and are each of cylindrical design. A collared bushing 28 is arranged around the second portion 23. The first portion 22 and the collared bushing 28 are seated in a socket 30 corresponding to their contour, which is embodied as a stepped bore. Here the bore is arranged in the so-called inner ring 32. The outer circumferential surface 34 of the inner ring 32 defines the radially inner limit of an annular flow duct 36 of the compressor 10. At the same time the inner ring 32 encompasses a rotor 35 of the compressor 10. At the radially outer ends (not shown) of the guide vanes 14, in a manner similar to the inner end 18, pivots are provided in a housing defining the outer limit of the flow duct 36.

The design chosen means that in principle the guide vanes 14 are merely inserted into the sockets 30 radially from outside. The radial direction here relates to the machine axis 38 of the compressor 10, along which this extends.

The inner ring 32 assembled from two segments 40 is represented schematically in FIG. 2. The two segments 40 each have an arc length of 180°. In a first connecting area 42 the two segments 40 are screwed together at the end face without leaving a gap. The other two ends 44 of the segments 40 are situated opposite one another in a second connecting area 46 forming a ring gap. The term ring gap is hereinafter abbreviated to gap 48. The second connecting area 46 is shown in detail in FIG. 3. A first socket 50, which in each case is formed by a blind hole, is provided in each of the two ends 44. The two first sockets 50 are situated opposite one another, so that an encapsulated spring element 52 is seated in these sockets. In the exemplary embodiment shown the spring element 52 is designed as a coil spring having a capsule 53. The spring element 52 is seated prestressed in the gap 48, so that the two ends 44 are forced apart. In the fitted state the inner ring 32 is thereby pressed against the pivots 26 of the guide vanes 14. A self-centering of the inner ring 32 is thereby achieved.

In a manner similar to the first sockets 50, sockets 54, which are likewise situated in opposing alignment with one another, are provided in the two ends 44. A centering element 56, which may be designed as a parallel key, for example, is seated in the second sockets 54.

This arrangement is capable of preventing a relative displacement of the two ends 44 in an axial direction, thereby locking the two ends 44. This prevents a shear stress load acting on the spring element 52.

The invention therefore relates overall to an axial-flow compressor 10 having an annular flow duct 36, in which adjustable guide vanes 14 of a vane ring extending through the flow duct 36 are pivotally mounted, wherein each guide vane 14 on the rotor side comprises a pivot 26 for mounting an inner ring 32 on its blade 16. In order to specify a self-centering inner ring 32 free from wear, the inner ring is embodied as a split ring having two opposing ends 44 and is provided with a spring element 52 for spreading the split ring. 

1.-9. (canceled)
 10. A compressor, comprising: a housing that defines a radially outer limit of an annular flow duct; and a vane ring comprising a plurality of guide vanes that extend radially through the annular flow duct and are pivotally mounted on the annular flow duct, wherein each of the guide vanes comprises a first pivot extending through the housing on the housing side and a second pivot extending into an inner ring on a rotor side of the compressor, and wherein the inner ring is a split ring having two opposing ends and is provided with a spring element for spreading the split ring.
 11. The compressor as claimed in claim 10, wherein the two opposing ends of the split ring comprise opposing first sockets in which the spring element is seated.
 12. The compressor as claimed in claim 10, wherein the spring element is encapsulated.
 13. The compressor as claimed in claim 10, wherein the opposing ends are axially locked.
 14. The compressor as claimed in claim 10, wherein the inner ring comprises at least two segments.
 15. The compressor as claimed in claim 14, wherein the inner ring or the segments are axially dividable.
 16. The compressor as claimed in claim 10, wherein a collared bushing is arranged on the second pivot.
 17. The compressor as claimed in claim 10, wherein the second pivot comprises a continuous circumferential groove in which a sealing ring is seated.
 18. A gas turbine, comprising: a compressor as claimed in claim
 10. 